Reflection and Transmission of Plane Elastic Waves at an Interface Between Two Double-Porosity Media: Effect of Local Fluid Flow

We obtain the reflection and transmission coefficients for inhomogeneous plane waves incident on a flat interface separating two double-porosity media described by the Biot-Rayleigh model, which takes into account the effect of local fluid flow (LFF). Three longitudinal and one transverse waves are reflected and transmitted, represented by potential functions specified by the propagation and attenuation directions. The continuity of the energy at the interface for sealed and open-boundary conditions yields a system of equations for the coefficients, and the expressions of the energy ratios for the reflected and refracted waves are derived in closed form. Numerical examples showing the magnitude, phase and energy ratio as a function of frequency and incidence angle are carried out to investigate the influence of the inhomogeneity angle, boundary condition, type of incidence wave and LFF effect. The results confirm that the LFF affects the reflection and transmission behaviors for the incident P1 and SV waves, irrespective of whether the interface is open or sealed. The effect causes interference fluxes between different waves, a consequence of energy conservation at the interface. We also perform full-waveform simulations to validate the results.